Fatigue life prediction of asphalt mixtures in the Brazilian indirect tension tests from the linear amplitude sweep binder data

This study compared the fatigue performance of one unmodified and two Brazilian commercial modified binders – SBS copolymer (AC+SBS) and recycled tire rubber (AC+rubber) – with their corresponding dense-graded asphalt mixtures. Linear Amplitude Sweep (LAS) tests at 19°C were conducted in the binders, while Indirect Tension (IDT) tests at 25°C were performed in the mixtures. The fatigue lives of binders (N_f) and mixtures (N) were determined in the LAS and IDT tests, and power correlations were fitted to the data. The AC+rubber showed the highest fatigue lives in both asphalt and mixture scales, and at least good correlations (R² > 0.83) between N and N_f were found. With respect to the parameter A₃₅ from LAS, it showed reasonable to excellent correlations (R² values from around 0.70 to 0.96) with the fatigue lives of mixtures. Overall, these findings give support to the use of LAS as an indicator of the fatigue resistance in the laboratory. In addition, the promising outcomes of IDT contribute to its use in the Brazilian mechanistic-empirical pavement design method (MEDINA). Further investigations with field test sections and other modification types of the binder may give new insights and allow comparisons between field and laboratory data.

Keywords:
SBS copolymer; Crumb rubber; Linear amplitude sweep; Fatigue life; Indirect tension test